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solved (with the exception of its charcoal) with a very powerful odor of hydrocyanic acid. The solution exhibited all the reactions of cyanide of potassium, and yielded 6·982 grms. of cyanide of silver, which dissolved (with decomposition) in fuming sulphuric acid, without leaving any residue of chloride of silver after being diluted with water. Hence we cannot for a moment demur to the following conclusion,-That a considerable quantity of cyanide of potassium is formed in iron furnaces immediately above the point where the blast comes in contact with the glowing fuel, and that it owes its formation to a direct union of carbon with potassium and nitrogen of the air.

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Our experiments have further shown that cyanide of potassium is volatile at high temperatures, and this property is of much influence in the part which it takes in the reducing process of the furnace. Carried up by the ascending current of gas, the cyanide of potassium, partly in a state of vapor, partly as a solid, reaches the region of the furnace in which the reduction is effected, and here it exerts its well-known reducing power. consequence of this it is decomposed into nitrogen, carbonic acid, and carbonate of potash, the former of which passes up with the ascending gaseous column to the mouth of the furnace, while the latter, not being volatile, falls back with the other materials in the furnace, to that point where it is again converted into cyanide of potassium, under the influence of the carbon and nitrogen. Hence a large quantity of ore may in this way be reduced in the lower part of the furnace, by comparatively a small quantity of regenerated cyanide of potassium. The importance of this view of the part played by cyanide of potassium, although previously entirely neglected, will be seen when we consider that this powerful reducing agent must ac cumulate in the furnace to a considerable extent. The region of the furnace where the highest temperature prevails forms a limited space, beyond which the cyanide of potassium cannot extend to the lower parts of the furnace, until its quantity is so much increased, by the potash descending in the materials supplied, that the excess of cyanide of potassium escapes volatilization and reaches the blast, where it is burnt and converted into nitrogen, carbonic acid, and carbonate of potash, the basis of which unites with the slag. We have already shown that the relation of the nitrogen to the oxygen in the gaseous mixture, collected only two and a half feet over the tuyère, is 79-2: 22.8, after deducting a quantity of oxygen corresponding to the hydrogen. If the gas generated at this place contained only the nitrogen and oxygen due to the air, the proportion would be 79.2: 20-8; and hence it follows that the gases at this point must either have obtained oxygen from a source independent of the air, or that a proportion of nitrogen has been abstracted from them. Any one who has had the opportunity of observing the temperature of the furnace at this part, will at once agree with the opinion that the excess of oxygen cannot be derived from the carbonic acid or iron ore. A simple inspection of the materials enables us to reject such an explanation as erroneous, for the fused materials flowing from the furnace do not evolve gas, although they come from a point in the immediate vicinity of that where the oxygen has been taken up.

We must, therefore, admit that this phenomenon is connected with the formation of cyanide of potassium in the furnace. The potash, as it yields

its oxygen to carbon during its conversion to cyanide of potassium, assumes for every volume of oxygen lost by it, two volumes of nitrogen in the form of cyanogen, and consequently the proportion of nitrogen to oxygen is necessarily increased.

Improved Portable Steam Hoisting Machines for Loading and Discharging Cargoes. By A. L. ARCHAMBAULT, Philadelphia.

This useful invention, of which the annexed cut is a representation, was built for Charles Bentric, a stevedore of Philadelphia, who has successfully tested it in discharging the cargoes of the ships Austria, Monongahela, and Hercules.

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The operation of the machine is briefly as follows:-The motion of the engine is communicated to the fly-wheel shaft S, which carries a small pinion gearing into the large wheel f; the winding barrel c, to which the hoisting rope is attached, is locked to the shaft of the wheelf by means of the driving friction coupling a, the latter being thrown into or out of action by the lever d; and the motion of the drum c, when free from the shaft of the wheel f, is controlled by the friction band b, which is tightened or slackened by the brake e.

The machine requires but a single person to keep up steam and attend to the brakes, and is capable of hoisting twelve hogsheads of tobacco from the hold of a vessel and turn them out on the wharf in ten minutes, or can discharge cotton at the rate of three hundred bales per hour. In case the hogshead or other article being raised should strike on the combings of the hatchway, the engineer has only to slacken the brake, and it is lowered, without stopping the motion of the engine, so as to clear the obstruction, and then, by drawing the lever of the brake tight again, the ascending motion is restored. The lowering brake is so arranged that a hogshead of tobacco can be suspended at any point required with the greatest ease. The machine being on wheels, is portable in its character, and can be moved about with a single horse.

A machine of this description should be procured by the stevedores of every sea port, California not excepted.

For the Journal of the Franklin Institute.

An Essay on the Physics of Steam. By THOS. PROSSER, C. E., New York. (Continued from page 136.)

That steam must be either saturated or surcharged will be readily admitted, and therefore, although the fact of its issuing from a high state of elasticity into the atmosphere, at the temperature due to saturated steam under that pressure, does not, per se, prove it to be surcharged, yet, taken in connexion with another fact, viz. that such steam does not scald the hand, affords certain proof that there is some physical difference between expanded steam and steam which has not been expanded; and as only two states of existence are known-saturated and surcharged-it necessarily follows that, on the score of probabilities, we are entirely justified in assuming that it is surcharged, in the absence of any reliable direct experiments on the subject.

It has been mentioned before that low pressure steam is a conductor of electricity, and I may now add that high pressure steam is a non-conductor,* but what bearing this has on the cause of expanded steam being surcharged it is difficult to say, in the present state of our knowledge of that most mysterious agent; whether, as the cause, in consequence of the electricity being converted into heat, which Pelsier has shown to be possible,† or simply as another effect of the same cause.

The electricity of effluent steam was first noticed by an engine-man at Seghill, about six miles from Newcastle, England. The first observations on the electricity of a jet of steam, while issuing from a boiler, is contained in a letter addressed by H. G. Armstrong, Esq., to Professor Faraday, and published in the 17th volume of the London and Edinburgh Magazine, Oct. 14, 1840. There are also some very interesting remarks on the same subject in this Journal, 3d series, Vol. I, p. 123. Evaporation is undoubtedly the great source of electricity in the atmosphere, as well as in the boilers of steam engines, and there appears nothing irrational or unphilo*Journal of the Franklin Institute, 3d series, Vol. 1, p. 123.

† Noad's Lectures on Electricity, p. 250, 408.

Noad's Lectures on Electricity, p. 252.

VOL. XVIII.-THIRD SERIES.-No. 3.-SEPTEMBER, 1849.

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sophical in supposing that the converse of this may also be true, knowing, as we do, that heat and electricity, if not identical in nature, are at least mutually convertible into each other.

When the electric spark is passed through oxygen and hydrogen gases, mixed in the proper proportions to form water, or as eight to one equiva lents, a flash is seen to pervade the whole mass, which is instantly changed and converted into steam at a pressure of 14 atmospheres, the temperature of which must therefore be in the neighborhood of 387° F., even on the supposition that the mixed gases are of the same density as saturated steam, the one at the common temperature, and the other at the elevated one; but how does the matter stand in this respect? 66 cubic inches of hydrogen gas will weigh 1.412 grs., and 33 cubic inches of oxygen gas will weigh 11.296 grs., or eight times as much, making together 12.708 grs. as the weight of 100 cubic inches. This is about the same weight as 100 cubic inches of steam at a pressure of 25 inches of mercury, and a temperature of 203° F.; but 14 atmospheres is equal to 420 inches of mercury, and if we imagine that the pressure will increase for each degree from 32°, we have the enormous temperature of 10,262° F., which is but 300° less than the reputed temperature of iron at a welding heat, before the required pressure is obtained; such is the energy with which electricity acts in composing water, when its constituents are thus brought into proximity. The decomposition of water is a very slow process, however, for it is reasonable to suppose that an equal amount of power is necessary, but there are no means known, by which sufficient energy of action can be produced to decompose a single drop of water, with anything like the rapidity with which the composition is effected. Hence it is difficult to imagine that the decomposition of water in a boiler can take place to any dangerous extent, even under the most favorable circumstances; but it is easy to see that if, under the combined influence of heat and pressure, free electricity should be generated, the sudden opening of a valve may scatter the water among the steam, and if, at the same time, the free electricity be converted into heat, we have ample reasons for expecting an explosion in any boiler so circumstanced, without approaching, except in a slight degree, the temperature which would appear necessary to decompose water.

MM. Jobard and Tassin support some such theory as this, and it does certainly account for many explosions that have taken place, and which no other does account for so rationally.

The cases alluded to are those in which there are several boilers in connexion, and which commonly explode simultaneously or nearly so, just as would be expected where the agent in operation was one of uncontrolable power. It appears to me that, to imagine free electricity as the effective agent in bursting boilers, in such cases at least, is far more rational than to assign it to free caloric, because dry or surcharged steam would appear to be particularly harmless, unless some such agent as electricity is brought to operate upon it, for, as steam, it must necessarily become surcharged by some means before it can be dangerous as an exploder, and the immense quantity of heat to be abstracted from the surcharged steam, and, if you please, from the red-hot boiler also, which disappears or becomes latent before steam of any great elasticity can be formed, precludes the idea of

so slow a process as evaporation must necessarily be, unless some new and more energetic medium than ordinary is brought into operation.

To give an illustration of this, let us imagine steam at 100 lbs. pressure to the square inch, the temperature of which will be 329-6° F., and the volume 293 times that of the water from which it was formed; now in order to double this pressure instantaneously, (for it must be remembered that it is almost thus that the most terrific explosions do occur: that is to say, when first set in motion after having been for a time in a state of rest,) it is necessary that 464 times as much water as that which already exists in such steam should be raised, together with itself, 54.8° F.; but this is a small part of the amount of the heat which must be abstracted to effect the contemplated change of elasticity, as 827.6° have disappeared or become latent in the fresh steam generated, being equal to 384° of the whole steam in the boiler, which is now at a pressure of 200 lbs. to the square inch, and temperature of 384.4°, occupying 147 times the volume of water from which it was generated; thus the whole heat which has to be developed instantly as it were, amounts to no less than 438.8° (54.8+384°). It is not very apparent how such an occurrence can take place by any wellknown and ordinary means, but if it did, one boiler might burst, but it is altogether inexplicable how all of a suite should follow, as though they were so exactly of the same strength that they must inevitably stand or fall together, which no one at all acquainted with the mechanical skill (or rather the want of it) of some of the western boiler makers, would for a moment suspect. It would rather appear to me that some subtle agent, such as electricity, must be in operation, whose power is so far beyond the elasticity of any boiler, that the strength of the metal of which it may be made is not of the slightest importance.

The electric theory does not appear to be in favor with Dr. Albans, in his very excellent work on the high pressure steam engine, as it may interfere prejudicially with his pet. The Doctor seems to have no opinion at all of steam at less than 8 or 10 atmospheres, to which, indeed, he appears to have descended out of deference to public opinion rather than to his own, as his "first love" was probably much higher, and he has coquetted with steam at 60 to 70 atmospheres pressure.

For the Journal of the Franklin Institute.

Side Wheels and Propellers for Sea Steamers.

As this city is justly entitled to the credit of having done more to introduce the screw propeller to the public than any other, it is but just that some of the numerous patentees of that article who reside here should demonstrate the advantages that mode of propelling has over the much abused side wheel. From reading the city items of our daily papers for two years past, I had supposed that side wheels, for sea steamers, were among the things that were, and that we should no more see those large wheel houses which, from propeller reports, were so very objectionable at sea. may judge of my surprise, when visiting New York, to find that all their sea steamers had side wheels, and that many more of the same kind were building. Being very well booked up on propellers, from reading the

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